Inhibitor



Patented Sept. 1, iaea HOE.

Stanley ll. Waugh, Westfieldl, N. .31., assignor to Tide Water Associated (ill Company, Bayonne, N. 1., a corporation of Delaware No Drawing. Application December 23, 1940, Serial No. 371,409

7 Claims.

This invention relates to chemical products effective to inhibit corrosion of metals, and more particularly to compositions containing said chemical products. In its more specific embodiments the invention is concerned with mineral oil compositions, particularly lubricants, containing said chemical products.

It is known that certain of the modern mineral oil lubricants are corrosive to metals such as steel under the conditions obtained in their use. In the lubrication of steel gears and the like, the gears and other metal machine parts are often maintained in contact with the lubricant for prolonged periods of time at elevated temperatures and under other conditions of operation promoting corrosive attackresulting in impairment of the useful functions both of the lubricant and the machine.

The exact reason for the stated corrosive action is not definitely known, but the efiect is generally believed to be caused by products of deterioration of the mineral oil or substances which have been added to the mineral oil for special purposes, or both. As an example of the latter type of lubricant, i. e., lubricants containing additive substances, there may be cited extreme pressure lubricating compositions. These compositions generally comprise a refined mineral lubricating oil and relatively minor amounts of substances effective to increase the load carrying characteristic of the oil to render the composition capable of lubricating gears, bearings and the like under the very high pressures existing between the contacting surfaces thereof in modern usage.

Of the many substances which have been proposed as additives to mineral oils to impart extreme pressure characteristics materials containing chlorine or sulfur have been widely used. Such additives are necessarily reactive in order that they may perform their intended function in the composition, the theory being that a load carrying film is formed on the contacting metal surfaces of gears and the like as a result of chemical reaction involving the extreme pressure constituent.

Certain of the extreme pressure constituents, however, are apparently too reactive and in addition to causing formation of the desired loadcarrying film also form products which alone or in conjunction with products of deterioration of the mineral oil result in the stated objectionable corrosion of the metal parts. This is particularly true of chlorine-containing lubricants.

The present invention is based upon the discovery that certain chromium-amine complex 55 compounds possess the property of efiectlvely inhibiting corrosion of metals; that said compounds may be incorporated in compositions, particularly in lubricant compositions, to be employed in contact with metal surfaces to stabilize said compositions and provide efiective protection of said surfaces against corrosive action. The inhibiting action of the stated compounds is especially eflicient against corrosive attack of chlorine-containing lubricants such, for example, as those of the extreme pressure type mentioned herelnabove. One important embodiment of the invention therefore relates to mineral oil lubricants containing chlorine having incorporated therein the stated chromium-amine complex compounds, and the invention will be illustrated and explained in reference to this specific phase.

The chrominum-amine complexes of this invention may be prepared by reacting chromium salts with certain amines. In one method of preparing them a water solution of a chromium salt, suitably an alkali metal chromate or dichromate, is prepared and to this solution there is added suflicient of an amine to precipitate the chromium-amine complex. Amines which I have found particularly suitable for the reaction are triethanolamine, triethylenetetramine, diethylamincethanol and cyclohexylamine. The

actual structure of the reaction product is not definitely known. The product is thought to be an addition compound of the chromium salt and amine of complex structure, possibly similar to the reaction products produced by reacting aqueous solutions of the salts of other metals and amines reported in Chemical Abstracts, vol. 28, page 1295 (1934), by A. Tettamanzi and B. Carli.

The chromium-amine complex prepared as described hereinabove may be incorporated in oils in any suitable manner. The complexes prepared from the amines specifically referred to above are substantially insoluble in mineral oil, and are preferably further treated to convert them to a form soluble in the oil. This may be accomplished by treatment of the complex with an organic acid or incorporation of the complex in the mineral oil in the presence of an organic acid. Suitable acids for this purpose are those of the type of naphthenic acids or the higher fatty acids such as olelc. In one procedure the complex, precipitated as stated hereinabove, is dried and added to a small portion of mineral oil. To this mixture there is added suflicient of the acid to bring the precipitate into solution. The acid apparently reacts with the precipitate ture of 180 F. during this time.

to term a reaction product which may be a soap of the chromium-amine compound. The stated chromium amine complex compounds produced by the reaction of chromates and amines, and those produced by reacting these reaction prodacts with acids, are novel so far as I am aware, and one phase oi the invention concerns the discovery of these new compounds.

The following examples illustrate the eflectiveness of the inhibitors of the invention in chlo-' rine containing mineral oil lubricants of the extreme pressure type. The test for determining portion which had been immersed in the oil to evidence no signs or corrosion. The portion which had contacted the water was only slightly -pitted. but the remaining surface of the pin corrosion inhibiting properties is a modification of the General Motors corrosion test described on pageD-ll of vol. II of General Motors Standards, April 1940. The General Motors corrosion test consists in putting a polished piece oi steel in a 50 cc. beaker containing cc. of distilled water and 25 cc. of the oil to be tested, covering the beaker with a watch glass and heating overnight at. a temperature between 160.F. and 190 F. The appearance of the steelaiter the test is the criterion of the corrosiveness of the oil tested.

Example I An extreme pressure lubricant composition containing byvolume of chlorinated petroleum wax, 15% by volume of suliurized corn oil and 70% by volume 01 a naphthenic base rcfined mineral oil distillate of 200 Saybolt seconds viscosity at 100 F. and color 2 to 3 A. S. T. M. was tested in the following manner:

Into a 50 cc. glass beaker were placed 5 cc. distilled water and cc. of the described extreme pressure lubricant composition forming a lower strata of water and an upper strata of oil. The test pin was positioned in the beaker so that a portion of its length was immersed in the water layer, a second portion in the oil layer and a third portion projected above the oil layer into the air. The beaker was then covered with a watch glass and heated for 24 hours, the

liquids therein being maintained at a tempera- At the expiration of this time the test piece was removed from the beaker and examined for corrosion. The steel test pin after this test showed the lubricant to be extremely corrosive. That portion of the pin which had been immersed in the water was deeply pitted while that portion which had been immersed in the oil was covered with a heavy. adherent coating of corrosion products resembling rust in appearance.

Example II A chromium-amine complex compound oi! this invention was prepared as follows:

To a saturated water solution (saturated at room temperature) of potassium chromate there was slowly added triethanolamine until the precipitate of chromium-amine complex no longer formed; The precipitate was filtered and dried at 210 F. and then added to about an equal volume oi. a refined petroleum distillate lubricating oil. Naphthenic acid was added slowly to the mixture until the precipitate had all dissolved in the oil. A clear solution resisted.

A composition comprising 5% by volume of this clear solution and 95% by volume of the extreme pressure lubricant of Example I was then prepared, the resulting composition containing the chromlumcomplex compound in solution was then subjected to the test described in Example I. Examination or the test pin at the expiration of the 24 hour test showed the showed no signs of corrosion.

Emmplc III The lubricant of Example I and the solution containing the chromium-amine complex compoimd described in Example II were mixed in the proportion 01 90% of the former and 10%01 the latter by volume. The resulting composition, containing the inhibitor in solution was tested as below, and this time the test pin after completion of the test showed no evidence 0! corrosion. The entire surface of the pin was free from pitting and was not coafedwith products oi corrosion.

The above examples clearly show the noncorrcsive character oi the oil compositions of this invention and particularly illustrate the ct-- iectiveness of the chromium-amine complex compounds described in chlorine containing lubricants. It should be understood, however, that the invention is not limited to lubricant compositions containing chlorine. The inhibitor compounds described herein are eflective in stabilizing oils containing other additive substances and in stabilizing highly refined or less highly refined oils, particularly those of mineral origin whether said oils contain additional added material or not. Likewise, the invention is not to be restricted to compositions intended for use as lubricants. For example, certain metal coating compositions are included in the invention. Typical of the latter are compositions which in use are applied to machine parts for the purpose of preventing corrosion in storage and transit.

Certain types of these compositions are known as slushing oils or anti-rust oils and generally contain a mineral oil material such as petrolotum. Some of these compositions have proven insufflciently eflective in preventing corrosion, due possibly to corrosive attack of the metals by products of deterioration of the constituents of the coating composition. It is contemplated according to this invention to incorporate relatively minor amounts of the described chromium-amine inhibitor in such coating compositions to efl'ect improvement in the corrosion inhibiting power thereof.

As examples of other compositions falling within the scope of the invention in which may be incorporated the described chromium-amine inhibitors to provide improved corrosion-inhibiting and other desirable characteristics may be mentioned greases and emulsifying (soluble) oils. Also considered within the scope of the invention are compositions comprising aqueous solutions of the described chromium-amine complex compounds. It has been found that incorporation of minor proportions of said products in such compositions provides efl'ective protection against corrosion of surfaces normally corroded by such aqueous compositions.

The proportions of the chromium-amine inhibitor compounds to be used depends upon the conditions under which they are to be employed and upon the particular type and composition of lubricant or other composition with which it is to be associated. The proportions shown in the above examples are not to be considered critical or limitative, since under different conditions and with different-compositions other proportions of inhibitors may be necessary.

lubricating oil, a minor proportion of a chlorine- I claim:

l. A lubricant composition comprising a mineral lubricating oil, a substance normally tending to cause corrosion of metal surfaces, and having dissolved therein, in minor proportion but in amount sufiicient to inhibit said corrosion, a substance prepared by the method comprising reacting a chromate with an amine and reacting the resulting product with an organic acid.

2. A lubricant composition comprising a mineral lubricating oil, a substance efiective to impart high load-carrying properties and in use normally causing corrosion of metal surfaces, and a minor proportion of a substance prepared by the method comprising reacting a chromate with an amine and reacting the resulting product with an organic acid, said proportion being sufiicient to inhibit said corrosion.

3. A lubricant composition adapted for the lubrication of bearing surfaces of gears and the like operating under high pressures comprising a major proportion of a mineral lubricating oil, a minor proportion of an extreme pressure agent and a minor proportion of a substance prepared by the method comprising reacting a chromium salt and an amine, said substance being efiective and in suflicient amount to inhibit the corrosion of metal surfaces normally attending the use of said lubricant composition.

4. A lubricant composition adapted for the lubrication of bearing surfaces of gears and the like comprising a major proportion of a mineral containing substance normally causing corrosion of metal surfaces and a minor proportion of a chromium compound efiective to inhibit said corrosion, said chromium compound having been.

prepared by the method comprising reacting a chromium salt with an amine and treating the resultant product with an organic acid.

5. A composition comprising a major proportion of mineral oil and ordinarily tending to corrode metal surfaces and having incorporated therewith a minor proportion of a chromiumamine complex in amount sufflcient to inhibit such corrosion.

6. A composition comprising a major proportion of mineral oil and ordinarily tending to corrode metal surfaces and having incorporated therewith a minor proportion of a chromiumamine complex in amount suificient to inhibit such corrosion, said complex being the product resulting from reacting a chromium salt witli an amine.

7. A composition comprising a major proportion of mineral oil and ordinarily tending to corrode metal surfaces and having incorporated therewith a minor proportion of a chromiumamine complex in amount sufiicient to inhibit such corrosion, said complex being the product resulting from the reaction of a chromium compound and an amine with an organic acid.

STANLEY P. WAUGH. 

